The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
For the last several years, dual clutch transmissions have represented a significant alternative to more conventional automatic motor vehicle transmissions which typically comprise several planetary gear sets, clutches and brakes. A defined sequence of engagement and disengagement of the clutches and brakes steps the transmission through the available gear ratios. In contrast to such direct, sequenced operation, a dual clutch transmission includes a pair of main clutches that alternately engage to provide torque through a previously selected gear pair disposed between a shaft driven by the clutch and a countershaft.
One of the drawbacks of dual clutch transmissions, especially when they include six, seven eight or more gear ratios is their axial length. Given certain motor vehicle platforms, axial length is critical and may limit the number of gears provided by a dual clutch transmission. Current market demand is for vehicles with relatively high numbers of gear ratios, i.e., seven, eight and higher and thus a vehicle with only five or six gears, though desirable from every other standpoint, may be viewed by the consumer as having lesser value. A second, though less apparent drawback of such transmissions, is their relatively high spin losses resulting from the large number of gears sets in constant mesh and rotation in spite of the fact that only one gear set at a time is active and transferring torque.
The present invention addresses these problems and provides a dual clutch transmission with reduced length and reduced spin losses.